The present invention relates generally to a compressed air supply system, a compressed air supply device for a vehicle, and a method of controlling an air compressor, which supplies a compressed air by the air compressor mounted in the vehicle.
Up to now, a device has been known in which when a compressed air discharged from an air compressor for a vehicle is accumulated in an air tank, and supplied to a load of the vehicle, in order to prevent the shortage of pressure in the air tank, the air compressor is switched to a load state according to a status of the vehicle or the course (for example, refer to Patent Literatures 1-4 mentioned below). A control device of Patent Literature 1 detects a pressure in the air tank, and puts the air compressor into the load state when it is discriminated that a brake is frequently used, on the basis of a change in the pressure.
Also, up to now, a device has been known in which in a configuration where the compressed air discharged from the air compressor mounted in the vehicle is accumulated in the air tank, and supplied to the load, a dryer having an adsorption agent (drying agent) that adsorbs moisture of the compressed air is disposed between the air compressor and the tank (for example, refer to Patent Literature 2). A device disclosed in Patent Literature 1 regenerates the adsorption agent while unloading the air compressor, thereby enabling the moisture in the compressed air to be continuously removed.
Further, a dew condensation water may be accumulated in the air dryer, and there is a risk that the dew condensation water is frozen within the air dryer during the cold months. Under the circumstances, up to now, there has been proposed a device in which a heater is disposed within the air dryer to eliminate the operation failure of the air dryer, which is caused by freezing (for example, refer to Patent Literature 3). However, in the configuration having the heater, a valve whose operation fails due to freezing is so heated as to be operable. However, there is a difficulty to prevent the freezing per se.
Also, there has been proposed a device that prevents freezing by discharging the dew condensation water with the use of a phenomenon that the dew condensation water within the air dryer is exhausted together with the compressed air, in the regeneration operation for regenerating the drying agent within the air dryer (for example, refer to Patent Literature 2). In the device of this type, because water per se that is accumulated in the air dryer is exhausted, freezing can be surely prevented.
The device disclosed in Patent Literature 4 regenerates the drying agent while unloading the air compressor, thereby enabling the moisture of the compressed air to be continuously removed.
Also, up to now, in a heavy vehicle such as a truck or a bus, there has been employed an air braking device using a compressed air as a working fluid that actuates a braking chamber. In the braking device of this type, a compressed air supply device for a vehicle which supplies a compressed air to each braking chamber is mounted.
The compressed air supply device for a vehicle includes an air compressor in which the compressed air discharged from the air compressor is accumulated in the air tank, and the compressed air within the air tank is supplied to each braking chamber as necessary. The air dryer having an adsorption agent (drying agent) that adsorbs moisture in the compressed air is disposed between the air compressor and the air tank (for example, refer to Patent Literature 4). The device disclosed in the Patent Literature 1 regenerates the adsorption agent while unloading the air compressor, thereby enabling the moisture of the compressed air to be continuously removed.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2003-276591
Patent Literature 2: Japanese Unexamined Patent Application Publication No. Sho-63(1988)-194717
Patent Literature 3: Japanese Unexamined Utility Model Application Publication No. Hei-01(1989)-77830
Patent Literature 4: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. Hei-5(1993)-505758